Double Ended Queue ADT using DLL

Algorithm to implement a double ended queue ADT of integers using Doubly linked list.

Algorithm to implement above program:

Initialize the front and rear nodes with NULL values

struct node *front=NULL,*rear=NULL,*cur,*temp

1. Algorithm for insertion at rear end:

Step 1: Create a new node

cur=(struct node*) malloc (sizeof (struct node))

Step 2: Read the content of node (cur->data)

Step 3: Assign new node right link to NULL

cur->right=NULL

Step 4: Assign new node to front & rear node 

Check if(rear==NULL&&front==NULL)

rear=front=cur

Step 5: otherwise

rear->right=cur

cur->left=rear

rear=cur

Step 6:stop

2. Algorithm for insertion at front end:

Step 1: Create a new node

cur=(struct node*) malloc (sizeof (struct node))

Step 2: Read the content of node (cur->data)

Step 3: Assign new node right link to NULL

cur->right=NULL

Step 4: Assign new node to front & rear node

Check if(rear==NULL&&front==NULL)

rear=front=cur

Step 5: otherwise

cur->right=front

front->left=cur

front=cur

Step 6: stop

3. Algorithm for deletion at front end:

Step 1: check if(front==NULL)

Print deQueue is empty

Step 2: otherwise

Check if(front==rear)

Print Deleted data is front->data

front=rear=NULL

Step 3: otherwise

temp=front;

print Deleted data is temp->data

front=front->right

front->left=NULL

free(temp)

Step 4: stop

4. Algorithm for deletion at rear end:

Step 1: check if(front==NULL)

Print deQueue is empty

Step 2: otherwise

Check if(front==rear)

Print Deleted data is rear->data

front=rear=NULL

Step 3: otherwise

temp=rear;

print Deleted data is temp->data

if(front==rear)

front=rear=NULL

rear=rear->left

rear->right=NULL

free(temp)

Step 4: stop

5. Algorithm for displaying the dequeue:

Step 1: check if(front==NULL)

Print deQueue is empty

Step 2: otherwise

temp=front;

repeat steps a-b until temp!= NULL

a. printf("%d ",temp->data)

b. temp=temp->right;

Step 3: stop

Thanks

Mukesh Rajput